In recent years, Japanese have consumed more of a Western diet, resulting in taking in excessive energy (increase in ingestion of fat and sucrose), and have had fewer chances for physical exercise. Therefore, the number of patients of lifestyle-related diseases such as obesity and diabetes continuously has increased. Under such social circumstances, prevention and amelioration of obesity is a key issue.
One of the methods for the preventing or ameliorating of obesity, that dieticians generally propose is to consume low-calorie or low-fat food. In recent years, it was reported that each of water-insoluble dietary fibers such as wheat bran, water-soluble dietary fibers such as indigestible dextrin, and resistant starches such as high amylose starch has an action of promoting lipid excretion (Non-Patent Document 1), an inhibitory action of sugar absorption (Non-Patent Document 2), and an action of reducing blood neutral fat (Non-Patent Document 3), respectively and these materials have an action of ameliorating glucose tolerance (Non-Patent Documents 3, 4 and 5). Thus, these materials are thought to be effective for the preventing or ameliorating of obesity.
Since a rapid rise in postprandial blood lipid level is thought to promote accumulation of fat, an approach of suppressing postprandial hyperlipidemia (increase in blood triglyceride level) is also a key issue for the prevention or amelioration of obesity. In recent years, there have been reported some safe and effective lipid-absorption inhibitors such as xanthan gum and propylene glycol alginate ester (Patent Document 1), chitosan (Patent Document 2) and a composition for ameliorating obesity containing an extract from animal meat and/or fish meat and a substance capable of suppressing fat accumulation, in combination (Patent Document 3).
It is also reported that sodium alginate, which is a high-molecular acidic polysaccharide found in brown algae, has an inhibitory action on increase in blood glucose level and thus is useful for the prevention of obesity and diabetes (Patent Document 4 and Non-Patent Document 7).
The aforementioned low-calorie food or low-fat food can exhibit a temporary effect of reducing body weight. However, since a food composing of the low-calorie food or low-fat food is generally not tasty (i.e., monotonous), such food becomes unacceptable by those who consume it over a long period, making long-term ingestion thereof difficult. Also, in order to attain the aforementioned physiological effect, the aforementioned conventional food materials such as water-insoluble dietary fiber, water-soluble dietary fiber, and resistant starch must be continuously ingested in a large amount over a long period of time. Although the physiological effect can be attained, suppression of obesity has not yet been confirmed. When foods and beverages are produced by using such food materials, their intrinsic appearance, taste, sensations such as touch to the teeth and smoothness are generally impaired. Therefore, the food materials cannot be easily incorporated into foods and beverages in a satisfactory amount, and a limitation is imposed on the type of the foods and beverages into which the food materials are added. In addition, difficulty is encountered in long-term ingestion of such foods and beverages.
Due to insolubility, making beverages containing water-insoluble dietary fiber is difficult. Resistant starch or water-soluble dietary fiber can be dissolved or dispersed in water. However, difficulty is also encountered in producing beverages containing resistant starch or water-soluble dietary fiber in a sufficient amount to expect anti-obesity effect, since the viscosity of the beverages increases.
Meanwhile, potassium alginate is widely used as a thickener for food and as a gelling agent incorporated into a dental impression material, and it is reported that a hypertension inhibitory action of potassium alginate based on active excretion of sodium in the body (Non-Patent Document 8).
However, potassium alginate has never been known to have an action of preventing or ameliorating obesity.